In this project, we hope to elucidate the mechanisms responsible for the pulmonary toxicity of paraquat, 1,1'-dimethyl-4,4'-dipyridylium dichloride, a herbicide which is extensively used in agriculture. Demonstration of a treatment for paraquat poisoning in rats should have clinical applications in the treatment of accidental paraquat poisonings in man. An understanding of the mechanisms involved in the pulmonary toxicity of paraquat should give insight into various mechanisms responsible for the development of pulmonary edema after exposure to other agents.